Reflex klystron assemblies



May 10, 1960 H. W. COCKRILL REFLEX KLYSTRON ASSEMBLIES 3 Sheets-Sheet 1 Filed Feb. 28, 1955 //Vl/ENTO/? H0570 M. (DC/(FILL BY g Arro/Fwsy y 1960 H w. COCKRILL 2,936,398

REFLEX KLYSTRON ASSEMBLIES Filed Feb. 28, 1955 3 Sheets-Sheet 2 Arrow 5y y 1960 H. w. COCKRILL 2,936,398

REFLEX KLYSTRON ASSEMBLIES Filed Feb. 28, 1955 3 Sheets-Sheet 3 ATTORNEY United States Patent REFLEX KLYSTRON ASSEMBLIES Huston W. Cockrill, Concord, Mass, assignor to Raythcon Company, Waltham, Mass., a corporation of Delaware Application February 28, 1955, Serial No. 490,762

9 Claims. (Cl. 315-5.19)

accuracy of concentricity of the focus (accelerating) grid, j

cathode and heater, accuracy of alignment of the electron gun elements with the cavity resonator and the repeller, and accuracy of spacing of the electron gun relative to the resonator and its associated grids.

The focus grid assembly of the electron gun consists essentially of at least one elongated grid sleeve which is apertured at one end and which is insulatedly mounted within a flanged mounting member. The grid assembly is removably attached, as by screws, to an anode or resonator block. This resonator block contains a centrally disposed recess into which a portion of the grid mounting member may be fitted. The recess may be tapered to form a portion of the beam-forming structure and may terminate in an aperture leading into the cavity resonator. A cathode assembly, including an electrically insulating base and a tubular element attached thereto, is brought into operating relationship with the grid assembly. The aforesaid tubular element is positioned about one end of the grid sleeve and connected thereto at the proper position, dependent upon the desired grid-cathode spacing. Proper spacing between the focus grid and the cavity resonator and suitable axial alignment thereof, is achieved by machining the contacting surfaces of the mounting member and the resonator block. The insulating base may contain a number of stakes brazed through apertures near the periphery thereof. These stakes provide support for the tubular element of the cathode assembly .and also permit attachment of flexible leads and lead-in conductors.

Another feature of the invention is that an electron gun may readily be removed from the discharge device merely by removing the screws or other means for mounting the electron gun to the resonator block.

An object of this invention is to devise means for obtaining extreme accuracy of concentricity of the grids and cathode of a klystron.

Another object of this invention is to provide for ac-- curate alignment of the electron gun of a klystron with the cavity resonator and the repeller, as well as accurate spacing 'of the 'klystron gun with relation to the cavity resonator and its associated grids.

A further object of this invention is to provide means for readily replacing the electron gun assembly of a klystron. i I 1 F In thedrawings:

Patented May 10, 1960 Fig. 1 is a central cross-sectional view of an embodiment of a velocity modulated electron discharge device embodying the subject invention;

Fig. 2 isa modification of the grid subassembly of Fig. 1;

Fig. 3 is a plan view of a portion of the cathode subassembly of Fig. 1;

Fig. 4 is a sectional view illustrating the manner of construction of the grid subassembly of Fig. 1;

Figs. 5 to 7 are sectional views illustrating the manner of machining the grid subassembly of Figs. 1 and 2; and

Fig. 8 is a sectional view illustrating a jig used in constructing the cathode subassembly of Fig. 1.

Referring now to Fig. 1, a portion of a velocity modulated electron discharge tube 5 of the type commonly known as a reflex klystron is shown. Tube 5 comprises essentially a resonator subassembly 7, a tuner assembly 8 including a reflector electrode 9 and an electron gun assembly 10 including a cathode subassembly 12, a cathode heater 14, and a grid subassembly 15.

Cathode subassembly 12 includes a cathode supporting sleeve 21 centrally mounted within an electrically insulating base 22 constructed, for example, of ceramic and provided with a number of small apertures 23 and 24, surrounding a large centrally disposed aperture 25 through which sleeve 21 extends. A number of short stiif wires or stakes 26 are inserted in apertures 24; a metallic collar 28 is supported, as by brazing, to the shorter stakes 26. A plurality of longer stakes 29 extends through base 22 and permits connection of flexible lead-in conductors 30 and leads from the various tube electrodes. If base 22 is made of ceramic, the walls of apertures 23 to 25 are preferably metallized to permit a firm ceramic-to-metal seal between the metallic sleeve 21 and stakes 26 and29. The actual sealing may be accomplished by means of copper solder rings, not shown, inserted around stakes 26 and 29 and sleeve 21. A tubular cathode member 32 is attached to cathode supporting sleeve 21 by means of one or more metallic connecting rods 33 which are spot welded, or otherwise connected, to both cathodemember 32 and cathode supporting sleeves 21, as shown in Figs. 1 and 2. A cathode emissive body 35 capable of copious thermionic emission is disposed within one end of cathode member 32. The cathode subassembly is not limited to the type shown in Fig. 1. For example, the cathode member 32 may itself be electron emissive instead of containing an electron emissive body 35. Also, the cathode assembly may comprise but a single tubular member. The cathode is connected to one of the elongated stakes 29 by a ribbon or connector 36 a portion of which is shown in Fig. 1.

The cathode is heated by means of a heater coil 14 made of a material, such as tungsten, which may be coated, if desired, with an aluminum oxide coating to prevent shorting of the individual coi-l turns and to insulate said coil from the walls of the cathode member 32. The extensions of the heater coil are brought through cathode supporting sleeve 21 and are connected either directly to a pair of elongated stakes 29, or to flexible metallic ribbons 39 which, in turn, are fastened to appropriate stakes 29. I

The grid subassembly 15 includes an inner grid sleeve 41, an outer grid sleeve 42 fitting over said inner sleeve, a channel 43 brazed or otherwise attached to said outer grid sleeve intermediate the ends thereof, and a mount-' consists essentially of a central hub portion 44? s ir-- rounded by a flanged portion 44". .l

Grid sleeves 41 and 42 are made preferably of a material having a low temperature coeflicient of expansion and both are made of the same material in order to prevent improper alignment resulting from inequalities of expansion. Grid sleeves 41 and 42 are fastened together by brazing, as shown at 47. Grid s'ubassembly is fastened to resonator assembly 7 by means of screws 48 inserted through aligned apertures in the grid mounting member 44 and resonator block 60, to be described subsequently. Insulation of the grids from resonator block 60 is provided by the annular insulator 45 previously described. If insulator 45 is made of ceramic, it is preferably metallized on the inner surface and a portion of the outer surface prior to brazing the insulator to the grid sleeve 45 and the grid mounting 44, respectively. Insulator 45 must then include a portion such as tapered portion 45' which is not metallized in order to provide an insulating gap between the grid sleeves and the resonator block. The electrons emitted from emitter are directed to the electron focussing lensformed by the apertures 51 and 52 in the ends of the respective inner and outer grid sleeves 41 and 42.

Although two grid sleeves with apertures of differing diameter are shown in Fig. 1, it is possible to replace these by a single grid sleeve having a tapered aperture therein, as shown in Fig. 2.

Grid subassembly 15 may further include a pair of shields 54 and 55. Shield 54 is afiixed to outer grid sleeve 42 at the end adjacent the grid aperture 52 and prevents the deposition of electrically conductive material emitted from the cathode onto the surface 45' of insulator 45. Likewise, shield 55, attached to the inner periphery of inner grid sleeve 41 at the end adjacent ceramic base 22 of cathode subassembly 12, prevents contamination of base 22 with electrically conductive material emitted from the cathode. A recess 20 in the base 22 tends to trap any material that may reach the base.

The resonator assembly 7 includes a resonator block consisting of a lower resonator body and an upper resonator body 62 hermetically sealed at the juncture 63. Lower resonator body '60, in addition to containing mounting holes 6-1, contains a centrally disposed recess 64 into which the hub portion 44' of mounting member 44 is adapted to fit snugly. Recess 64 is tapered, as shown in Fig. 1, and terminates in a restricted aperture or resonator grid 65. Resonator grid 65, which has a centrally disposed portion substantially frustoconical in shape, with its smaller diameter at the upper end thereof, and resonator grid 66 spaced from resonator grid 65, form a resonator gap. A diaphragm 71 serves to define partially the shape of cavity resonator 68. Upper resonator body 62 carries a centrally apertured shaped plate 70, which acts as a radio frequency choke to prevent radio frequency leakage from resonator 68.

Tuning of the klystrons may be accomplished by vary ing the spacing between resonator grids and 66, and thereby varying the resonant frequency of resonator 68. The tuning means includes a tuner sleeve 77 and a flexible membrane or bellows 75 sealed to the envelope 76 of the klystron and to the tuner sleeve. Energy is extracted from resonator 68 by means of a rectangular waveguide 80, one of whose inner surfaces is tapered to provide a satisfactory impedance match between the klystron and an external load over the band of frequencies desired. A tubular metallic -member 82 is afiixed at one end to a flanged portion of lower resonator body 60 and the other end of this sleeve is secured to a glass envelope 84 through one end of which lead-in conductors 30 extend externally of the tube.

Although means for tuning the klystron is shown in Fig. 1, it should be understood that this invention is not limited to tubes whose frequency is variable, but may be incorporated in fixed frequency velocity modulated electron discharge devices.

A typical method of manufacturing the electron gun assembly is shown in Figs. 4 to 8. Although the following explanation deals with an electron gun assembly using a grid sleeve of the type shown in Fig. 2, the same procedure may be used in the case of a compound grid sleeve of the type illustrated in Fig. 1. If a compound grid sleeve is employed, the inner and outer grid sleeves 41 and 42, respectively, are first brazed together, as at 47.

Grid sleeve 40 is inserted into the deepest recess 102 of jig 101, as shown in Fig. 4. Channel 43 is inserted about grid sleeve 40 and seats against step 103 of the jig. A solder ring 104 then is positioned in contact with channel 43. Insulator 45 is inserted over grid sleeve 40 and rests against ledge 105 formed in the periphery of said sleeve. Finally, mounting member 44 is placed in position with the flanged portion 44" seating against step 106 of the jig. Solder rings 108 and 109 are dropped into the positions indicated in Fig. 4 and serve to connect the ceramic insulator 45 to mounting member 44 and grid sleeve 40. After brazing insulator 45 to mounting member 44 and grid sleeve 40, the grid subassembly 15 is removed from the jig and is machined accurately in a manner now to be described.

Grid sleeve 40 is inserted in chuck 110 in the manner shown in Fig. 5 and surface 112 of the mounting memher is machined.

Grid subassembly 15 is then removed from chuck 110 and reinserted in the chuck so that the chuck jaws engage the machined surface 112, as shown in Fig. 6. With the setup shown in Fig. 6, surfaces 81, and 91 are accurately machined, in order to insure that the axis of the grid assembly coincides with the axis of the chuck. Surface 90 of grid sleeve 40 is machined so as .to provide a sliding fit with the inner surface 97 of cathode collar 28. It will be noted that surfaces 112, 90 and 91 are concentric.

Grid subassembly 15 is then removed from chuck 110 and is reinserted in the position shown in Fig. 7, that is, with machined surface 91 gripped by the jaws of chuck 110. In the setup of Fig. 7, surface 92 of the hub portion 44 of mounting member 44 is machined to fit surface 93, the annular boundary of recess 64, of lower resonator body 60, thereby limiting axial displacement of the gun structure 10 relative to the resonator assembly 7. Also with the setup of Fig. 7, surface 94 of flanged portion 44 of mounting member 44 is machined so that when grid subassembly 15 is secured to resonator assembly 7, the upper surface of grid sleeve 40 is properly spaced from surface 96 of resonator grid 65. While grid subassembly 15 is still chucked on surface 91, grid aperture 50 (apertures 51 and 52 of the compound grid sleeve of Fig. l) is bored.

The internal surface 97 of cathode collar 28 must be jigged axially with outer surface 98 of cathode member 32; furthermore, the distance between upper surface of base 22 and the uppermost surface 99 of cathode emis-sive body 35 must also be jigged so that the correct cathode to grid spacing is obtained. This may be accomplished by means of a jig such as shown, by way of example, in Fig. 8. Jig 120 includes a lower member 122 and an upper member 124 supported in spaced relationship with respect to lower member 122 by means of several posts 125 secured by screws 126. Jig 120 includes a chuck 128 which is more or less conventional. Jig 120 further includes an adjusting rod 130, a portion.

of which thread-ably engages the upper member 124 and terminates at one end in a portion of reduced size. The other end of the adjusting rod 130 is provided with an enlarged head 132 which, if desired, may be slotted to permit access of a screwdriver.

Cathode member 32 is inserted within the chuck jaws g until the end of member 32 containing cathode body 35 seats against the end of adjusting rod 130. The lower member 122 of jig 120 is provided with a recess 132 and Contains an aperture 133 permitting insertion of cathode sleeve 21. Cathode collar 28 is inserted about an elongated portion 135 of lower member 122 and is accommodated within recess 132. The uppermost surface of base 22 engages surface 123 of member 122. A plurality of connecting rods 33 is secured, as by brazing, to one end of cathode sleeve 21. The inner surface 97 of collar 28 is adapted to fit closely against the outer surface 137 of portion 135. Since the surface 137 of lower member 122 is coaxial with the inner surface of the jaws of chuck 128, the inner surface 97 of cathode collar 28 is concentric with the surface 98 of cathode member 32. The desired spacing between surface 99 of cathode body 35 and the uppermost surface 95 of the grid sleeve (see Fig. 1) is obtained by turning the adjusting rod 130 until the proper degree of insertion of cathode member 32 within the jaws of chuck 128 is achieved. When the proper spacing has been obtained, the cathode member 32 is chucked on surface 98 and the three ends of connecting rods 33 are brazed to the end of the cathode member protruding from the chuck. The brazing apparatus may be brought in between the upper and lower members of jig 120 in the space between posts 125.

Cathode subassembly 12 is next removed from the jig 120. Cathode collar 28 is inserted over the grid sleeve 40 (outer grid sleeve 42 of Fig. 1), as shown in Fig. l. The flanged portion 28' of cathode collar 28 is spot welded to channel 43 of the grid snbassembly 15, thus providing a springy contact which permits collar 28 to seat properly against the upper surface 100 of base 22.

If the grid sleeve should prove to be slightly too long to seat properly against base 22, a small amount of material may be removed from the end of the grid sleeve.

Because the cathode member 32 and the grid are fitted together coaxially and since the grid and the resonator block recess 64 are in alignment, the cathode emitter, focus grid aperture or apertures, and resonator grids are accurately aligned. By fabricating the electron discharge device in the manner above described, the concentricity and spacing between the various elements are held to very close tolerance.

. This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is: V

1. A reflex klystron comprising a cathode assembly including an electron-emissive cathode fixedly mounted within a cathode element, said cathode assemblyfurther including a cathode sleeve coaxial with said cathode element, a focussing grid assembly including at least one elongated grid sleeve containing an aperture at one end thereof and having a longitudinal axis, a mounting member positioned adjacent said one end of said grid sleeve and including a hub portion, a flanged portion having a machined mounting surface, and electrically insulating means positioned between said grid sleeve and said hub portion and securely attached to said grid sleeve and said hub portion, said insulating means, said grid sleeve and said hub portion forming an integral unit; a resonator block containing a cavity resonator, said resonator block including a centrally disposed recess having a peripheral portion contacted by the-hub portion of said mounting member, said machined surface of said mounting member directly contacting said resonator block of said flanged portion over an extended region disposed adjacent said one end of said grid sleeve as measured along said longitudinal axis, and means for resiliently attaching said grid sleeve to said cathode Sleeve.

2. A reflex klystron comprising a cathode assembly including an electron-emissive cathode body, a supporting member for said cathode body fixedly mounted in an electrically insulating base, and a tubular element aflixed to said base, a focussing grid assembly including at least one elongated grid sleeve containing an aperture at one end thereof, a mounting member positioned adja' cent said one end of said grid sleeve and including a hub portion, a flanged portion, and electrically insulat ing means positioned between said grid sleeve and said hub portion; a resonator block containing a cavity reso nator, said resonator block having a centrally disposed recess terminating at one end in a sleeve portion and terminating at the other end in a centrally located apertured resonator grid concentric with said sleeve portion, the hub portion of said mounting member being in direct contact with said sleeve portion, said flanged portion of said mounting member directly contacting said resonator block over an extended region adjacent said one end of said grid sleeve, and means for resiliently attaching said grid sleeve to said tubular element.

3. A reflex klystron comprising a cathode assembly including a cathode supporting member fixedly mounted in an electrically insulating base, an electron-emissive body maintained in fixed position relative to said supporting member, and a tubular element affixed to stakes from said resonator, said resonator block having a cen trally disposed annular recess terminating at one end in a sleeve portion and terminating at the other end in a centrally located apertured resonator grid concentric with said sleeve portion, a portion of said mounting member being in direct contact with said sleeve portion, means for removably attaching said mounting member to said block, said tubular element surrounding and slidably engaging said grid sleeve, and means for resiliently attaching said grid sleeve to said tubular element.

4. A reflex klystron comprising a cathode assembly, a focussing grid assembly including at least one elongated grid sleeve containing an aperture at one. end thereof, said grid sleeve having a longitudinal axis, a mounting member having a hub portion surrounded by a flanged portion, and electrically insulating means positioned be tween said grid sleeve and said hub portion, a resonator block containing a cavity resonator, and output cousaid mounting member engaging said sleeve portion for axial alignment of said grid sleeve and said resonator grids, said flanged portion of said mounting member directly contacting said resonator block over an extended region disposed adjacent said one end of said grid sleeve as measured along said longitudinal axis.

5. A method of fabricating a velocity modulated electron discharge device including a resonator block containing a centrally disposed recess therein consisting of a cylindrical portion and a tapered portion terminating in a resonator aperture, comprising the steps of securing an elongated grid sleeve in electrically insulating relationship with a grid mounting member consisting of a hub and a flange extending radially from said hub and having a surface adapted to contact said resonator block, clamping said mounting member, machining a first portion of said hub, machining the outer surface of said grid sleeve until the outer diameter of said grid sleeve is substantially equal to the inner diameter of a cathode element, unclamping said mounting member, clamping said mounting member about said machined first portion, machining a second portion of said hub until said hub seats within the cylindrical portion of said recess, machining said surface of said flange until the desired spacing between said grid sleeve and said resonator aperture is obtained, removably securing said mounting member to said resonator block, jigging a cathode emissive member axially with said cathode element, adjusting the relative position of said cathode member and said cathode element during jigging corresponding to the desired spacing between said cathode member and said grid, securing said cathode member to said cathode element, discontinuing said jigging, positioning said cathode element about said grid sleeve and in sliding contact therewith, and resiliently attaching said cathode element to said grid sleeve.

6. A method of fabricating a velocity modulated electron discharge device including a resonator block containing a centrally disposed recess therein consisting of a cylindrical portion and a tapered portion terminating in a resonator aperture, comprising the steps of securing an elongated grid sleeve in electrically insulating relationship with a grid mounting member consisting of a hub and a flange extending radially from said hub and having a surface adapted to contact said resonator block, clamping said mounting member, machining a first portion of said hub, machining the outer surface of said grid sleeve until the outer diameter of said grid sleeve is substantially equal to the inner diameter of a cathode element, unclamping said mounting member, clamping said mounting member about said machined first portion, machining a second portion of said hub until said hub seats within the cylindrical portion of said recess, forming an aperture in one end of said grid sleeve, machining said surface of said flange until the desired spacing between the apertured portion of said grid sleeve and said resonator aper ture is obtained, removably securing said mounting memoer to said resonator block, securing said cathode element to an electrically insulating base, jigging a cathode emissive member axially with said cathode element, adjusting the relative position of said cathode member and said cathode element during jigging corresponding to the desired spacing between said cathode member and the apertured portion of said grid, securing said cathode member in a fixed position relative to said base, discontinuing said jigging, positioning said cathode element about said grid sleeve and in sliding contact therewith, and resiliently attaching said cathode element to said grid sleeve.

7. A method of fabricating a velocity modulated electron discharge device having a cathode assembly includ ing a cathode element attached to an insulating base and a cathode emissive body, a grid assembly including a grid sleeve and a mounting member consisting of a hub and a flange disposed substantially normal to said hub, and a resonator block having a centrally disposed annular recess adapted to receive a first portion of said hub and tapering into a resonator aperture, comprising the steps of fixedly securing said grid sleeve in electrically insulating relationship with said grid mounting member, clamping said flange and machining a second portion of said hub and the outer surface of said grid sleeve, clamping said machined second portion of said hub and machining said first portion of said hub until said first portion is substantially of the same size as said recess, ma-

chining said flange to obtain a desired spacing between said grid assembly and said resonator aperture, unclamping said machined grid assembly, removably attaching said mounting member to said resonator block, axially jigging said cathode body and said cathode element, attaching said cathode body and said cathode element during jigging, discontinuing said jigging of said cathode assembly, positioning said cathode element about said grid sleeve in sliding contact therewith, and resiliently securing said cathode element to said grid sleeve.

8. A method of fabricating a velocity modulated electron discharge device having a cathode assembly including a cathode element attached to an insulating base and a cathode emissive body, a grid assembly including a grid sleeve and a mounting member consisting of a hub and a flange disposed substantially normal to said hub, and a resonator block having a centrally disposed annular recess adapted to receive a first portion of said hub and tapering into a resonator aperture, comprising the steps of fixedly securing said grid sleeve in electrically insulating relationship with said grid mounting member, clamping said grid sleeve, machining the periphery of said flange, clamping the periphery of said flange and machining a second portion of said hub and the outer surface of said grid sleeve, clamping said machined second portion of said hub and machining said first portion of said hub until said first portion is substantially of the same size as said recess, machining said flange to obtain a desired spacing between said grid assembly and said resonator aperture, concentrically boring an aperture in said grid sleeve, unclamping said machined grid assembly, removably attaching said mounting member to said resonator block, axially jigging said cathode body and said cathode element, attaching said cathode body and said cathode element during jigging, discontinuing said jigging of said cathode assembly, positioning said cathode element about said grid sleeve in sliding contact therewith, and resiliently securing said cathode element to said grid sleeve.

9. A reflex klystron comprising a cathode assembly including an electron-emissive cathode fixedly mounted within a tubular element, a focussing grid assembly including at least one elongated grid sleeve containing an aperture at one end thereof; amounting member positioned adjacent said one end of said grid sleeve and including a hub portion, a flanged portion having a machined mounting surface, and electrically insulating means positioned between said grid sleeve and said hub portion and securely attached to said grid sleeve and said hub portion, said insulating means, said grid sleeve and said hub portion forming. an integral unit; and a resonator block containing a cavity resonator, said resonator block including a centrally disposed recess having a peripheral portion contacted by the hub portion of said mounting member, said machined surface of said hub portion of said mounting member directly contacting said resonator block.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 936398 May 10 1960 Huston W0 Cockrill n the printed specification It is hereby certified that error appears 1 e said Letters of tlie above numbered patent requiring correction and that th Patent should read as corrected below.

Column 5 line 71 strike out "of said flanged portion" and insert the same after "surface" in line 69 same columna Signed and sealed this 11th day of April 1961.,

(SEAL) Attest:

ERNEST SWDER ARTHUR W. CROCKER Attesting Oflicer Acting Commissioner of Patents 

